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Debug Guide

System3 Block Diagram

The figure above is a block diagram of System3. The various elements have the following functions:

The System Computer runs the System3 server software, which is invoked by clicking on the Run Sys3 icon. The server controls the setting of switches and the powering of blocks by communicating with the Interface Message Processor (the IMP). The System Computer also runs the SCab display program that provides a graphical user interface invoked by clicking (only once!) on the SCab icon. Although not part of System3, the TMRC2 Windows PC can monitor network traffic for debugging purposes via the Pic_test program. It also can access files on the System Computer ("Drive Y") via the Ethernet.

The IMP is a very specialized network card/device that performs two very important functions:

The Switch Card Bus protocol and electrical characteristics are discussed at http://tmrc.mit.edu/sys3/switchcard. The Switch Cards control the status of all track switches and lineside signals.

The Network Cards are of several types:

Further information about the Switch Card Bus, Switch Cards, and various types of Network Cards can be found at http://tmrc.mit.edu/sys3. Many of the applicable web pages are also included in the "Web Info" section at the back of this binder.

Topology of the System3 Network

When debugging System3 problems, there are many occasions when one needs to know the topology of the System3 network. This information is available from three sources:

TMRC System 3 Bus Addresses

On the System Computer, (TMRC), you can find C:\Home\TMRC\Sys3 development\SYS3 Bus Addresses. It looks like this, but this is just a sample of what it looks like. This is not the updated list.

TMRC System 3 Bus addresses

Note: cards are listed in order of distance from the IMP Addresses are not significant in card location.

Number Card Type (numeric) Card type Location
0 1 IMP Under tower
99 4 Turntable Engine yard
240 3 Cab driver F yard, east end
7 2 Block card Helix
8 2 Block card Helix
9 2 Block card Helix
135 5 B'ville control panel Berkmannville
241 3 Cab driver Berkmannville
11 2 Block card Under staging
12 2 Block card Under staging
242 3 Cab driver Foot of tower
3 2 Block card Cable storage area
243 3 Cab driver Oil plant
2 2 Block card Cable storage area
4 2 Block card Cable storage area
5 2 Block card Cable storage area
17 2 Block card Under roundhouse
1 2 Block card Under roundhouse
9 2 Block card Under roundhouse
10 2 Block card Under roundhouse
102 8 F yard controller F yard, west end
13 2 Block card Under F yard (left)
14 2 Block card Under F yard (left)
15 2 Block card Under F yard (left)
16 2 Block card Under F yard (left)
19 2 Block card Under F yard (2nd cabinet)
244 3 Cab driver Middle Heights
245 3 Cab driver F yard, west end

Troubleshooting a Network Card

Once you have identified a suspect card, the first thing to do is to confirm that this is the correct suspect card.

First, and most obvious, confirm that the suspect card is getting power. If not, jiggle the power connectors. If that doesn't help, check the four power lights at the top edge of the tower nearest the System Computer and Windows PC. If any of these is out, cycle the system power off and on to reset the circuit protectors within the power supplies. Also check the manual circuit breakers under the tower to ensure that none of these has tripped.

If the suspect card is apparently getting power, reconnect it to the network and jiggle the network connectors. Restart Sys3 and see if this solves the problem.

If the problem affects only one block on the card, there is a possibility that the connection of the track feeders for that block has become loose. Check this.

Block Card Debug Aids

Each block card serves eight blocks. The throttles for those eight blocks are mounted on a heat sink along one side of the card. At the end of the card nearest the throttles is a connector for the voltages used on the card. On older cards, the voltages are:

On newer cards, the voltages are:

There are two sets of LEDs near the throttles. The red ones are labeled “Reverse” on the board. When lit, each indicates that the corresponding reverse relay is operated; the train is westbound. Two LEDs near the end of the package are labeled “+5” and “+12.” When lit, they indicate that the block card is receiving those voltages.

The green LEDs are labeled “DCC Select.” When lit, each indicates that the corresponding DCC selection relay has been operated; that block is connected to the (as yet unimplemented) DCC bus. The end-most LED is labeled “Status” and is the “heartbeat” LED. When lit, it indicates that the on-board processor is running.

In one corner of the board there are two RJ45 connectors, one black and one silver. (On older boards these are mounted on an auxiliary board.) The silver connector contains a cable that connects “upstream” (via other boards) to the IMP. The black connector contains a cable that connects “downstream” (via other boards) to the network terminator resistors. The silver connector contains a green LED that shows signalling activity going toward the IMP. The yellow LED on that connector shows signalling activity coming from the IMP.

The cables typically pass over a set of yellow LEDs labeled “Speed.” The brightness of each LED is proportional to the voltage being applied to the corresponding block. The two yellow LEDs at the end of the package are software debug LEDs.

There is one other set of connectors on the board - the track power leads. Blue wires go to the North rails and Orange wires go to the South rails

Determining Which Block Card Powers Which Block

As an aid to operators, the block numbers shown on the SCab display are designated in a fashion that indicates their location. For example, block GC102 is in or near Gifford City; block FY12 is in or near the Freight Yard, etc. The block numbers shown on the display (called "dnames") are not the same as those used in the block card documentation. This has the advantage that a particular block on the layout can be moved to a different block card without changing its name on the display. However, it also means that debugging a problem with a particular block requires that you translate between the block number shown on the display and the block number used in the block card documentation.

There are three methods of doing the required translation:

Note: If you Ctrl-click on a block that is shown as a thin gray line rather than the customary white, green, red, or pink, this indicates that the block has not been implemented or that system cannot communicate with the block card for that block.

Determining Which Switch Card Powers Which Switch

Unlike the SCab display block numbers, which are designated in a location-descriptive fashion, the switch numbers shown on the display are the same numbers that are used in the switch card documentation.

There are two methods of determining which switch card controls a particular switch:

Note: If you Ctrl-click on a switch that is shown as a gray oval rather than the customary white, this indicates that the switch has not been implemented or that system cannot communicate with the switch card for that switch.

The Real.lay File

At tmrc/sys3/server/real.lay there is a file that provides a substantial amount of information about System3.

The Relationship Between Blocks and Switches

The first section of real.lay describes the relationship between blocks and switches. As described in http://tmrc.mit.edu/sys3/scab/scabops.html, turnout switches each have three connections, numbered 0, 1, and 2. Connection 0 is the base of turnout, connection 1 is the normal route through the switch and connection 2 is the route that will be followed when the switch is operated. A crossover switch adds a fourth connection, number 3, connected to number 2 when the switch is in the normal position.

The real.lay file uses the above nomenclature to describe which blocks are connected to points 0, 1, 2, and 3 (if provided) for each switch. A typical entry in this section is:

Crossover S131

Connect 0 B194 1

Connect 1 B192 0

Connect 2 B191 0

Connect 3 B193 1

Note: In some cases where there are switches close together, there will be a short stretch of track between switches that does not have its own block, but rather is powered by another block depending on the state of the switches. Such a "block" is referred to as a "swing block" and is designated by an S-number.

Connectivity in Various Sections of the Layout

Real.lay begins with a list of connections in Berkmannville:

Block B131 {

connect 0 S122 1 (The 0 end of Blk 131 connects to the 0 end of Sw 122)

connect 1 B193 0 (The 1 end of Blk 131 connects to the 0 end of Blk 193)

Block B132 {

connect 0 S122 2 (The 0 end of Block 132 connects to the 2 end of Sw 122)

connect 1 B194 0 (The 1 end of Block 132 connects to the 0 end of Blk 194)

Crossover S122 {

connect 0 B126 1 (The 0 end of Xover S122 connects to the 1 end of Blk 126)

connect 1 B131 0 (The 1 end of Xover S122 connects to the 0 end of Blk 131)

connect 2 B132 0 (The 2 end of Xover S122 connects to the 0 end of Blk 132)

connect 3 S121 1 (The 3 end of Xover S122 connects to the 1 end of Sw 121)

hand right

Switch S121 {

connect 0 B127 1 (The 0 end of Sw S121 connects to the 1 end of Blk 127)

connect 1 S122 3 (The 1 end of Sw S121 connects to the 3 end of Sw 122)

connect 2 none (There is no connection to the 2 end - presumably a siding)

hand right

The real.lay file contains similar information for Middle Heights (Middletown), Freight Yard mainline, Freight Yard, Turntable, Gifford City, P-Yard, and Staging Yard. Similar information for some of the switchcards is also included.

Which Switch Cards Control Which Switches

The next section shows which switch cards control which switches.

Typical entries are:

SwitchCard 1 {

switches 0 {S33 S34 S35 S55 S36 S37 S71 S72}

input 0

}

SwitchCard 2 {

switches 0 {none S39 S51 S30 S28 S29 S31 S32}

input 0

}

SwitchCard 3 {

switches 0 {none S53 S52 S73 S25 S26 S27 S49}

signals 1 {none 5 (S28-1 0) S1 (S27 1) S1 (S27 2) S1}

input 0

The switch numbers shown are the same as the switch numbers shown on the Scab display. Note that some of the switch cards also drive wayside signals. The listing indicates the number of signal heads and where located.

Which Block Cards Control Which Blocks

The next section shows which block cards control which blocks.

Typical entries are:

BlockCard 2 {

blocks {B11 B12 B13 B21 B22 B23 none B32}

}

BlockCard 3 {

blocks {BX5 BX6 none none none none B26 B27}

}

BlockCard 4 { <P>blocks {B10 B14 B20 B31 B24 none none none}

}

BlockCard 5 {

blocks {B34 B35 B43 B44 B45 B46 none none}

A Sample Listing of the Order of Cards on the Network

This listing begins as:

Card: 0 Card Type: 1

Card: 240 Card Type 3

This is only a sample listing, is marked as a comment, and should be ignored. The file "TMRC System 3 Bus addresses" is more informative and more up to date,

A Sample Listing of the Sys3 Debug Console

The next section of real.lay is an example of the status report that is produced on the System Computer when System3 starts up. Like the "sample listing of the order of cards," this is not real-time information. However, some comments about the information shown might be useful.

For example:

Card: 0 Type: 1 (imp) Uptime: 0 seconds Reset: 0

Card: 245 Type: 3 (protocab) Uptime: 0 seconds Reset: 4 Overflows: 0 Overtime: 0

Card: 8 Type: 2 (block) Uptime: 443 seconds Reset: 4 Overflows: 0 Overtime: 0

Uptime is measured from is a four-byte quantity that measures the time since the last reset in 60th of seconds. The values shown is not particularly important for debugging purposes. Rather, what is important is the fact that the number changes.

Reset - The kind of reset the card last had (power on, brownout, etc.

Overflows - Whether the receiver serial port has had any overflows.

Overtime - Whether we took too long going around the software loop.

Translating Block Card Block Numbers to Display Block Numbers

The final section of real.lay is a list that translates block numbers from the block cards into display names (dnames). Typical entries are:

B10 BGC109

B11 BGC107

B12 BGC106

Thus, block card blocks B10, B11, and B12 correspond to display blocks GC109, GC107, and GC106 respectively. As their prefix indicates, they are all in Gifford City.

Operating a Hardware Cab

Assigning a Train to a Hardware Cab

(Telling System3 which train you want to run and which cab (control box) you want to use.)

At the SCab display, click on the block containing the train that you want to run. A dialog box will appear. The dialog box includes a list of hardware cabs that are available, i.e. plugged in and not yet in use by some other operator. Choose a cab by clicking on the small box next to the desired cab number.

Operating in "Switching Areas," the Default Mode for Hardware Cabs

In the 105th Street area, the Freight Yard (East and West), Middle Heights, and Berkmanville (East and West), the switch layouts are sufficiently complex that an entrance-exit (NX) control system is used. It is basically a case of "I'm here and I want to go there." Each of the aforementioned locations contains a card with a diagram of the switching area and a switching area identifying area code, such as #19.

By entering the area code, the operator is now ready to select a number from the left side of the drawing followed by a number on the right side of the drawing. The control system will then set up a route between those two points. For example, the diagram for the 105th Street area is shown below:

Available Hardware Cab Commands in a Switching Area

  • * = Reverse
  • 07 = drop block behind
  • 09 = steal block ahead (traditionally called "call on")
  • # = prefix for selecting another switching area

Entering 1 then 2 will set up a route from the point marked 1 on the left to the point marked 2 on the right. The route will use the leftmost crossover. Entering 1 then 4 will set up a route between the same two points, but the route will use the rightmost crossover.

Performing Switching Operations In Other Areas

When progressing from one of the switching areas discussed in the preceding section to another, enter #99, as that is the code for non-area switching. The following hardware cab commands are available: (New ones are shown in italics).

Available Hardware Cab Commands Outside a Switching Area

  • * = Reverse
  • 1-6 = throw 1st-6th facing point switch ahead. Counts from center of a block. With multi-block train, use of 7 may be required to ensure that count is done from loco block.
  • 7 = drop block behind
  • 8 = throw blocking switch
  • 9 = steal block ahead
  • # = prefix for selecting a switching area

Using a hardware cab to perform switching operations in areas other than those listed above is a bit more complex, as it becomes very important to know where the centers of the various blocks are and to know which of the cars in your train "occupy."

Consider the following case:

A train arriving from right to left, has uncoupled between cars A and B so that it can drop car A on the siding served by switch 108. If the operator enters a "1" without having reversed the locomotive, switch 100 will throw, as that is the next facing point switch ahead of the train. The more interesting possibilities are summarized in the following tables:

Operator pressed a "7" (drop behind) before reversing Car B and/or C occupies Neither B nor C occupies
Track between 100 and 108 is a separate block from track between 108 and 127 Pressing 1 throws 108 Pressing 1 throws 108
If the tracks between 100 and 108 and between 108 and 127 are all one block, "7" has no effect, as there is no "behind." Pressing 1 throws 108 Pressing 1 throws 108

Operator reverses without pressing "7" Car B and/or C occupies Neither B nor C occupies
Track between 100 and 108 is a separate block from track between 108 and 127 Pressing 1 throws 127 Pressing 1 throws 108
Tracks between 100 and 108 and between 108 and 127 are all one block, with the block center between 100 and 108. Pressing 1 throws 108 Pressing 1 throws 108

After dropping the car on the siding, reversing to pull out of the siding, and passing over switch 108, the operator can reverse one more time, enter a "1" to re-line switch 108 for the main, and proceed to pickup cars B and C. It will probably be necessary to enter a "9" (steal block ahead) to move forward into the block containing cars B and C.

Had the train upon its original arrival found switch 108 thrown against it, the operator could have entered an "8" (throw blocking switch) to throw switch 108 into the desired position.


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